Production of metal salts of organic acids



United States Patent 3,133,942 PRODUCTION OF METAL SALTS OF ORGANIC ACIDS Edgar Hahl, Ludwigshaien (Rhine), Germany, assignor to Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine), Germany No Drawing. Filed Dec. 1, 1961, Ser. No. 156,507 Claims priority, application Germany Dec. 3, 1960 5 Claims. (Cl. 260414) This invention relates to the production of metal salts of organic acids. More particularly, it relates to the production of salts of aliphatic, aromatic and cycloaliphatic carboxylic acids of metals having a normal potential between 0.80 and +0.5 volt. I

It is known that metal salts of organic acids can be prepared by dissolving oxides, hydroxides or carbonates of metals in carboxylic acids and isolating the salt from the solution by evaporation or cooling. When starting from the metals themselves, especially the more noble metals which are below iron in the electromotive series, these must first be dissolved in an inorganic acid and then precipitated as carbonates and separated before they can be reacted with organic acids. This method has the disadvantage that it requires a number of stages and often only yields neutral compounds when special precautions are observed; such neutral compounds are often required, for example when the salts are to be used as catalysts.

According to another known method, metal salts of organic acids may be prepared by the direct action of the acids on the metals. Naturally this method is limited to metals having a negative normal potential. Even with metals of this'group, however, this method does not lead to satisfactory results because often it requires reaction periods of considerable length, especially with the more noble metals of this group.

It is an object of the present invention to provide an improved method for the production of salts of aliphatic, aromatic and cycloaliphatic carboxylic acids with metals having a normal potential between 0.80 and +0.5 volt in a single operation. Further advantages of the invention will be apparent from the following description. These objects are achieved by reacting a metal having a normal potential between 0.80 and +0.5 volt in pulverulent form with the carboxylic acid which may be diluted with water or an inert organic solvent and which serves at the same time as a solvent for the salt to be prepared, at a temperature between room temperature and the boiling point of the acid used in the presence of gases containing free oxygen and if desired separating the salt formed from the resultant solution by cooling.

All aliphatic, aromatic or cycloaliphatic carboxylic acids may be used. Saturated aliphatic monocarboxylic acids with l to 8 carbon atoms, especially acetic acid and propionic acid, are particularly suitable for the process. Salts of higher unsaturated fatty acids, as for example oleic acid, may however also be prepared according to this invention.

The acids may be used either as such or, when pos-sible, also in the form of their aqueous solutions. Inert organic solvents, i.e. those which are stable under the reaction conditions and are miscible with the acids used, may also be employed as diluents. Examples are 'y-lactones, for example 'y-butyrolactone, nitriles, for example acetonitrile, propionitrile and benzonitrile, and alkylene carbonates, for example ethylene carbonate and propylene carbonate. The amount of vcarboxylic acid may be varied between an equivalent amount in relation to the metal used and an excess of up to 40 moles.

9 If the reaction is carried out with equivalent amounts, it is advantageous to work in the presence of a solvent 3,133,942 Patented May 19, 1964 with which the acid used is miscible in order that the reaction may be carried out in the liquid phase.

All metals having a normal potential lying within the above-specified limits of --0.80 and +0.5 volt may be used. The metals nickel, cobalt, copper and lead, with which the salts of the divalent stage are formed, are especially suitable for the reaction. In the case of metals with which salts of the trivalent stage are formed, as for example bismuth and iron, it is necessary to take into ac count the property of these salts of hydrolyzing in weakly acid and aqueous medium and thus forming insoluble basic salts. When using acids diluted with water in these cases the reaction should be carried out in a pH range Within which no hydrolysis takes place. 0n the other hand, such hydrolysis provides the simple possibility of preparing in one operation for example the salt of a di valent metal, as for example nickel, and freeing it at the same time from impurities, as for example iron.

The process according to this invention may be carried out batchwise or continuously by suitable regulation of the supply of acid and withdrawal of salt solution. The salt can be obtained from the resultant salt solution, if desired by cooling. The temperatures to be used may be varied between room temperature and the boiling point of the acid in question provided the acid does not decompose at this temperature. It is advantageous to Work at temperatures between and 200 C., especially at 90 up to 120 C. The process may be carried out at atmospheric pressure or at increased pressures up to about 10 atmospheres.

The oxygen-containing gas required as oxidizing agent is advantageously led through the reaction solution at such a rate that about to of the oxygen contained therein is used up. It is preferred to use air or pure oxygen as the oxidizing gas.

To shorten the reaction period it is advantageous to add activators to the reaction solution. Aldehydes, ketones and acid anhydrides are suitable for this purpose. Especially favorable results as regards reaction period are achieved by adding as activators the bromides of the metals to be reacted. The said bromides may also be formed in situ, by adding to the solution the carbonates of the metals in question together with compounds serving as a source of bromine ions, such as hydrogen bromide or tetrabromoethane. The same results can be achieved by adding elementary bromine to the reaction mixture. The

activators are used in an amount of 0.1 to 5% by weight Example 2 10 grams of nickel powder is treated with 200 g. of a 50% by weight aqueous solution of propionic acid under the conditions specified in Example 1. 0.2 g of nickel bromide is added as activator. The reaction is ended after 3 hours.

Example 3 A suspension of 15 g. of nickel powder and 0.3 g. of nickel bromide in 200 g. of 40% by weight acetic acid is treated at C. as described in Example 1. The reaction is ended after 3 /2 hours. The solution is then cooled to room temperature and the crystals deposited are separated by filtration. After drying, 46 grams of nickel(Il) acetate, Ni(C H O ).4I-I O (Ni found: 23.60%, cala culated: 23.58%) is obtained. This is a yield of 72.5% of the theory. The nickel concentration of the filtrate is 2.6%.

Example 4 20 g. of cobalt powder is treated with 200 g. of 50% by weight acetic acid, as described in Example 1. Reaction is discontinued after two hours. By cooling the reaction mixture to room temperature, 28 g. of cobalt(II) acetate Co(C- H O .4H O (Co found: 23.40%, calculated 23.67) is obtained. This is a yield of 38.6% of the theory. Conversion, with reference to the cobalt introduced, is 86%. The cobalt content of the filtrate is 4.7%.

Example 5 When reacting 15 g. of cobalt powder with 185 g. of 30% by weight propionic acid under the conditions specified in Example 1, the cobalt dissolves within 1% hours. By cooling the reaction mixture, filtering and drying the filtered product, 24 grams of anhydrous cobalt(II) propionate (Co found: 28.68%, calculated 28.74%) is obtained. This is a yield of 46% of the theory. The remainder of the cobalt is in the filtrate.

Example 6 A suspension consisting of 568 g. of 11.3% by weight aceti cacid, 32 g. of cobalt powder containing 0.2% by weight of iron and 0.3 g. of cobalt bromide as activator is treated at 100 C. by passing 30 liters per hour of air therethrough. When the reaction is ended after ten hours, the hot reaction mixture is filtered off from the insoluble iron(III) hydroxide formed at the same time. A solution of cobalt acetate of about 16% by weight strength is obtained.

Example 7 Example 6 is repeated under the same conditions with 568 g. of 14% by weight propionic acid instead of acetic acid. Complete separation of iron can also be achieved in this case.

Example 8 200 g. of n-butyric acid and 20 g. of copper powder are treated for 1% hours with oxygen while being slowly heated to 100 to 115 C. and while being stirred. After the product has been cooled, filtered and dried, 39 g. of copper(II) butyrate (Cu found: 26.70%, calculated: 26.74%) is obtained. This is a yield of 52% of the theory, 5.4% of dissolved copper is present in the filtrate.

Example 9 185 g. of n-valeric acid is treated with 15 g. of copper powder for three hours under the conditions specified in Example 1. 41 g. of copper(II) valerate (Cu found: 23.75%, calculated: 23.91%) is obtained from the reac tion mixture, representing a yield of 73% of the theory With reference to a conversion of 89%.

Example 0 187 g. of n-caprylic acid and 13 g. of copper powder are heated at a temperature of 100 to 110 C. for 2 /2 hours in the presence of oxygen. A conversion of 79% is achieved. After working up the reaction mixture, 50 g. of copper(II) caprylate (Cu found: 18.15%), calculated: 18.18%) is obtained. This is a yield of 88% of the theory.

Example 11 A mixture of 9 g. of lead powder, 0.2 g. of lead bromide and 191 g. of a-ethylhexanic acid is oxidized by the action of oxygen at about 90 C. as described in Example 1. After five hours, the whole of the lead has passed into solution with the formation of lead ethyl hexanate.

Example 12 A suspension of g. of bismuth powder and 190 g. of 100% propionic acid is treated with oxygen at 135 C.

4 as described in Example 1. The whole of the bismuth has been oxidized after threehours.

Example 13 A mixture of 6.3 g. of copper powder, 24.5 g. of benzoic acid and 200 g. of 'y-butyrolactone is treated with oxygen for an hour while stirring and heating to about 160 C. The product is cooled, filtered and dried and 23.5 g. of copper(II) benzoate (Cu found: 20.91%, calculated: 20.78%) is obtained. This is a yield of 78% of the theory. 0.6% of dissolved copper is present in the filtrate.

The same result is achieved by using the same amounts of acetonitrile or ethylene carbonate as solvent instead of butyrolactone.

Example 14 Air under a gauge pressure of 5 atmospheres is passed in an amount of 350 liters per hour (measured after the relief valve at 20 C. and 1 atmosphere absolute) into a stirred suspension of 0.36 kg. of cobalt powder in 5.7 kg. of 13% by weight acetic acid contained in a pressure vessel provided with a reflux condenser, while heating the vessel slowly to C. Oxidation is ended after four hours. A solution containing about 18% by weight cobalt acetate is obtained.

Example 15 A suspension consisting of 195 g. of propionic acid and 5 g. of tin powder is treated with pure oxygen at a temperature of 30 C. under the conditions specified in Example 1. After 20 minutes the whole of the tin has passed into solution with the formation of tin(II) propionate.

Example 16 Example 18 A mixture consisting of 5 g. of chromium powder, 1 ml. of 48% by weight hydrobromic acid and 195 g. of n-butyric acid is treated with pure oxygen at C. under the conditions specified in Example 1. After 6 hours all of the chromium is oxidized with the formation of chromium(III) n-butyrate.

Example 19 A mixture consisting of 12 g. of cobalt powder, 0.1 g. of cobaltous bromide and 108 g. of oleic acid is treated as described in Example 1 at 100 C. with pure oxygen. After 2 /2 hours all of the cobalt has passed into solution with the formation of cobalt(II) oleate.

Example 20 7 g. of nickel powder, 0.1 g. of nickel bromide and 193 g. of 75% by weight formic acid are treated with pure oxygen at 100 C. under the conditions specified in Example 1. After cooling the resulting solution to room temperature, 15 g. of nickel(II) formiate is separated by filtration. The nickel concentration of the filtrate is 0.3% by weight.

What I claim is:

1. A process for the production of an organic acid salt which comprises reacting a pulverulent metal having a normal potential of -0.80% to 0.5 volt with an organic acid selected from the group consisting of saturated aliphatic monocarboxylic acids of 1 to 8 carbon atoms, oleic acid and benzoic acid at a temperature from about room temperature up to the boiling temperature of said organic acid, in the presence of free oxygen and in the presence of an activator consisting of the bromide of said metal.

2. A process as claimed in claim 1 wherein said metal bromide activator is used in an amount of 0.1 to 5% by weight with reference to the metal being reacted.

3. A process as claimed in claim 2 wherein the organic acid employed in the reaction is diluted with water.

4. A process as claimed in claim 2 wherein the organic acid employed in the reaction is diluted with an inert organic solvent selected from the group consisting of v-lactones, nitriles and alkylene carbonates.

5. A process as claimed in claim 2 wherein the reaction temperature is about 50 C. to 200 C.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR THE PRODUCTION OF AN ORGANIC ACID SALT WHICH COMPRISES REACTING A PULVERULENT METAL HAVING A NORMAL POTENTIAL OF -0.80% TO 0.5 VOLT WITH AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF SATURATED ALIPHATIC MONOCARBOXYLIC ACIDS OF 1 TO 8 CARBON ATOMS, OLEIC ACID AND BENZOIC ACID AT A TEMPERATURE FROM ABOUT ROOM TEMPERATURE UP TO THE BOILING TEMPERATURE OF SAID ORGANIC ACID, IN THE PRESENCE OF FREE OXYGEN AND IN THE PRESENCE OF AN ACTIVATOR CONSISTING OF THE BROMIDE OF SAID METAL. 